The present invention relates to vehicle engine cooling systems, and more particularly, to such systems of the type including a liquid-to-air heat exchange device and a temperature-responsive fan drive for rotating a cooling fan, and drawing air through the heat exchange device.
In a typical vehicle engine cooling system of the type to which the present invention relates, the radiator includes a coolant inflow tank at the top, and a coolant outflow tank at the bottom. These tanks are arranged in such a manner that there is continuous and approximately equal flow of coolant from the top tank to the bottom tank, across the entire width of the radiator As a result, the temperature of the ambient air flowing through the radiator is typically the same across the entire width of the radiator.
Although the conventional radiator arrangement, as described above, has been considered generally satisfactory, there have been certain performance shortcomings of the conventional cooling system. As one example, when a vehicle is traveling along the road, with the fan drive disengaged, then stops such as at a traffic light, the velocity of the air flowing through the radiator decreases substantially. As a result, the temperature of the air rises, even though the temperature of the coolant has typically not risen above the temperature requiring operation of the fan drive. As the air temperature rises, the fan drive begins to operate in the engage condition, thus substantially increasing the fan noise and the engine horsepower consumed.